Field
Exemplary embodiments relate to a liquid crystal photo-alignment agent, a liquid crystal photo-alignment film manufactured using the same, a method of manufacturing the same, and a liquid crystal display including the liquid crystal photo-alignment film.
Discussion of the Background
A liquid crystal display, which is one of the most common types of flat panel displays currently in use, typically includes two panels having field-generating electrodes, such as a pixel electrode and a common electrode, formed thereon, and a liquid crystal layer interposed therebetween. The liquid crystal display may generate electric fields in a liquid crystal layer by applying voltage to the field-generating electrodes, and may change the direction of liquid crystal molecules of the liquid crystal layer according to the generated electric field, thereby controlling polarization of incident light so as to display images.
The two panels constituting the liquid crystal display may include a thin film transistor array panel and a counter display panel. In the thin film transistor array panel, a gate line for transferring a gate signal and a data line for transferring a data signal may cross each other, and a thin film transistor connected to the gate line and the data line, a pixel electrode connected to the thin film transistor, and the like may be formed. A light blocking member, a color filter, a common electrode, and the like may be formed in the counter display panel. However, the light blocking member, the color filter, and the common electrode may alternatively be formed in the thin film transistor array panel.
In a typical liquid crystal display, in order to use liquid crystals as an optical switch as set forth above, the liquid crystals may be initially aligned in a predetermined direction on the innermost layer of a display cell on which the thin film transistor is formed. To this end, a liquid crystal photo-alignment film is typically used.
The liquid crystal photo-alignment film may direct the arrangement of the liquid crystal molecules to set a direction when the liquid crystals are moved by an electric field to form an image. Generally, in order to obtain uniform luminance and a high contrast ratio in the liquid crystal display, the liquid crystals are uniformly aligned.
As a general method of aligning the liquid crystals, a rubbing method including applying a polymer film such as polyimide on a substrate such as glass and rubbing a surface in a predetermined direction by fibers such as nylon or polyester is used. However, in the rubbing method, when the fibers and the polymer film are rubbed, fine dust or electrical discharge (ESD) may occur, which may cause serious problems when a liquid crystal panel is manufactured.
In order to solve problems inherent in the rubbing method, a photo-alignment method in which anisotropy is induced to the polymer film by light radiation instead of friction thereby arranging the liquid crystals using anisotropy has been researched.
Generally, in the photo-alignment method, an alignment layer including a photo-alignment (photo-reactive) polymer is formed under the liquid crystal layer and linearly polarized UV is radiated on the alignment layer to cause a photo-reaction. As a result, the photo-alignment in which main chains of the photo-alignment polymer are arranged in a set direction occurs, and the liquid crystals included in the liquid crystal layer may be aligned by the photo-aligned alignment layer. However, the photo-alignment polymer described above has drawbacks in that structural and thermal stabilities of a polymer main chain are poor and alignment and the generation of afterimages remain problematic.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.